Gas turbine power plant

ABSTRACT

A gas turbine power plant with no intercooler for compressed air includes a compressor, a combustor for burning fuel with compressed air from the compressor to produce combustion gas, a turbine driven by the combustion gas, a generator driven by the turbine to generate electric power, a regenerative heat exchanger which heats the compressed air with the heat of exhaust gas of the turbine and has a water spray arranged therein for spraying water droplets onto the compressed air therein, and a spray device directly communicating with the compressor for spraying water onto compressed air of high temperature from the compressor to humidify the compressed air, the compressed air being led to the regenerative heat exchanger.

BACKGROUND OF THE INVENTION

The present invention relates to a gas turbine power plant which isprovided with a turbine driven by combustion gas having a high moisturecontent and a heat recovery system for recovering the heat of turbineexhaust gas and, more particularly, to a gas turbine power plant whichcomprises a compressor not employing any intercooler for compressed air,a combustor burning fuel with compressed air, a turbine driven bycombustion gas of a high moisture content and a heat recovery system forrecovering the heat of turbine exhaust gas, in which the moisturecontent of the combustion gas is increased by increasing a quantity ofwater or steam contained in air compressed by the compressor to besupplied into the combustor.

Conventional gas turbine power plants using humidified air are disclosedin many publications. For example, JP B 1-31012 and JP A 9-2641582 eachdisclose a gas turbine cycle in which air compressed by a compressor andliquid phase water used as a heat recovery medium and heated arecontacted with each other in a exchanging tower, thereby to obtainhumidified air or an air/steam mixture and cooled liquid phase water,and the humidified air recovers the heat of turbine exhaust gas whilethe cooled liquid phase water serves as a heat recovery medium torecover the heat of turbine exhaust gas and intercool the compressor,wherein the liquid phase water of a quantity corresponding to a quantitytransferred to the compressed air as steam is used as a cooling mediumdownstream of the intercooler of the compressor cooled by the cooledliquid phase water obtained in the exchanging tower or humidificationtower, and makes up the liquid phase water used in the exchanging towerand served for heat recovery.

JP B 1-19053 discloses a gas turbine system which effects heat recoveryof turbine exhaust gas or the turbine exhaust gas heat recovery andintercooling of a compressor with humidified air or compressedair/water/steam mixture, obtained by injection of liquid phase waterinto the compressed air at a compressor outlet, without using such anexchanging tower or humidification tower as disclosed in the JP B1-31012 and JP A 9-264158, and cools beforehand the compressed air usedfor forming the above-mentioned humidified air with a part of thehumidified air.

Further, “J. of Eng. for Gas Turbine and Power, vol. 117, pp 499-508(1995)” by P. Chiesa, et al. and ASME Paper 96-GT-361 “Revap Cycle: ANew Evaporative Cycle Without Saturation Tower” by J. De Ruyck, et al.also disclose a gas turbine system not using a humidification tower asdisclosed in JP A-1-19053.

However, the above-mentioned conventional techniques do not consider tofurther increase a quantity of water or steam contained in the airheated by the heat of exhaust gas from the gas turbine.

Namely, an upper limit of a water quantity that humidified air cancontain, that is, a water quantity (hereunder, referred to as saturatedwater quantity) that saturated air contains depends on temperature, andthe higher the temperature of the humidified air, the more the saturatedwater quantity. Therefore, even for the air humidified until it becomesa saturated condition (a relative humidity ψ, which denotes a partialpressure of steam in the humidified air to a saturated pressure of steamcorresponding to temperature of the humidified air, =1) at an inlet of aheat recovery apparatus, the relative humidity becomes low by beingheated in the heat recovery apparatus and having been raised intemperature. That is, for the humidified air which has been raised intemperature in the heat recovery apparatus, it is possible to furthercontain therein steam until it reaches a saturated condition.

Further, there are many other prior art references examples of which areas follows:

WO 98/01658 discloses a method and device for generation of mechanicalwork and heat in an evaporative gas turbine process in which all or partof compressed air is humidified and cooled and then led to a heatrecovery apparatus, but no water is injected onto the compressed airinside the heat recovery apparatus.

EP 821136 A1 and EP 821137 A1 each disclose a system for powergeneration in which water cooling means is provided on a compressor orat an upstream side of the compressor to inject water into air beingcompressed or before compression to cool the air. In the system, a waterinjection device is not provided a heat recovery apparatus.

JP A 6-248974 discloses a partially regenerative type, two fluid gasturbine which is provided with a mixer for mixing compressed air andsteam to humidify the compressed air, but is not provided with a wateror steam injection device in a heat exchanger for heat-exchanging aturbine exhaust gas and the compressed air from the mixer.

JP A 10-103080 discloses a gas turbine cycle in which water is sprayedonto air being compressed to cool the compressed air, but the compressedair is not humidified in a recovery unit.

EP 0718472 A1 discloses a power process utilizing humidified combustionair to a gas turbine in which a saturator tower is provided to humidifycompressed air and the humidified air is transferred to a heat recoveryunit without any water injector and, alternatively, compressed air froma high pressure compressor is transferred to a heat recovery unit with aspray nozzle and water is injected onto the compressed air only in theheat recovery unit.

ASME Paper 95-CTP-39 “Humid Air Cycle Development Based on EnergyAnalysis and Composite Curve Theory” by J. De Ruyck, et al. discloses agas turbine cycle, where heat exchange or heat recovery is effected atan intercooler, an aftercooler and a heat recovery system of hightemperature exhaust gas. Compressed air from a high pressure compressoris cooled in the aftercooler by a cooling medium flowing in a conduitinside the aftercooler. The cooling medium is a part of the compressedair from the high pressure compressor, which is humidified and cooled byinjection of feedwater into the conduit of the aftercooler. A part ofcompressed air is transferred to the heat recovery system after beingsupplied with feedwater and heated by the compressed water in theaftercooler. The other part of the compressed air is transferred fromthe aftercooler to the heat recovery system without feedwater supplybefore entering the heat recovery system and supplied with feedwaterinside the heat recovery system.

In this system, there is room for improvement on temperature lowering ofthe compressed air before entering the heat recovery system.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a gas turbine powerplant in which the power generation efficiency is improved by increasinga flow rate of a turbine working medium such as combustion gas bysufficiently increasing the water content of the air to be supplied to acombustor, and increasing a heat quantity recovered from exhaust gas ofthe gas turbine.

Another object of the present invention is to provide a gas turbinepower plant which has no intercooler for compressed air and lesscomplicated structural parts and which is improved in power generationefficiency by increasing a flow rate of a turbine working medium such ascombustion gas by supply of air of increased water content to acombustor, and increasing a heat quantity recovered from exhaust gas ofthe gas turbine.

The objects are attained by a gas turbine power plant according to thepresent invention, which has no intercooler for compressed air andcomprises a compressor, a combustor for burning fuel with compressed airfrom the compressor to produce combustion gas, a turbine driven by thecombustion gas, a generator driven by the turbine to generate electricpower, a regenerative heat exchanger which heats the compressed air withthe heat of exhaust gas of the turbine and has a water spray arrangedtherein for spraying water droplets onto the compressed air therein, anda spray device directly communicating with the compressor for sprayingwater onto compressed air of high temperature from the compressor tohumidify the compressed air, the compressed air being led to theregenerative heat exchanger.

The gas turbine power plant is provided with a feedwater heaterdownstream of the regenerative heat exchanger with respect to a flow ofexhaust gas from the turbine, and the above-mentioned water spray andspray device each are supplied with feedwater heated by the feedwaterheater.

Further, the present invention resides in a gas turbine power plantwhich comprises a compressor for compressing air to discharge compressedair, a combustor for burning fuel with the compressed air to producecombustion gas, a turbine driven by the combustion gas, a generatordriven by the turbine to generate electric power, a regenerative heatexchanger for heating compressed air to be supplied to the combustorwith the heat of exhaust gas of the turbine, the regenerative heatexchanger having a water spray arranged therein for spraying waterdroplets onto the compressed air therein, a first flow line of a part ofcompressed air from the compressor, leading to the regenerative heatexchanger, a heat exchanger arranged on the first flow line for loweringtemperature of the compressed air in the first flow line, a first spraydevice arranged on the first flow line downstream of the heat exchangerand upstream of the regenerative heat exchanger, a second flow line ofanother part of compressed air from the compressor, fluidlycommunicating with the heat exchanger, a second spray device arranged onthe second flow line for spraying water onto the compressed air flowingin the second flow line and humidifying the compressed air to turn it tohumidified air lowered in temperature, the humidified air beingheat-exchanged with the compressed air from the first flow line in theheat exchanger.

In this gas turbine power plant, preferably, flow rates of compressedair in the first and second flow lines are substantially the same aseach other.

This gas turbine power plant is provided with a third spray device onthe second flow line downstream of the heat exchanger, and thehumidified air by the third spray device is led to the regenerative heatexchanger.

Further, this gas turbine power plant is provided with a feedwaterheater downstream of the regenerative heat exchanger with respect to aflow of exhaust gas from the turbine, and the above-mentioned waterspray and first, second and third spray devices each are supplied withfeedwater heated by the feedwater heater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a mechanical system showing a gasturbine power plant of a first embodiment of the present invention;

FIG. 2 is a diagram showing relations of plant efficiency and plantoutput to spray quantities of water in the regenerative heat exchangerin FIG. 1;

FIG. 3 is a diagram showing a relation of exhaust gas temperature at thefeedwater heater outlet to spray quantities of water in the regenerativeheat exchanger in FIG. 1;

FIG. 4 is a diagram for explanation of arrangement of spray nozzles ofthe regenerative heat exchanger in FIG. 1;

FIG. 5 is a schematic diagram of a mechanical system showing a gasturbine power plant of a second embodiment of the present invention;

FIG. 6 is a schematic diagram of a mechanical system showing a gasturbine power plant of a third embodiment of the present invention;

FIG. 7 is a schematic diagram of a mechanical system showing a gasturbine power plant of a fourth embodiment of the present invention;

FIG. 8 is a graph showing a relation between the plant efficiencyincrements % (relative value) and flow rate ratios of compressed air Aato total compressed air from the compressor (Aa/A(=Aa+Ab)); and

FIG. 9 is a graph of humidifying and temperature loweringcharacteristics for explaining plant efficiency in comparison with thepresent invention and a prior art.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention will be described hereunder,referring to the drawings.

First of all, an embodiment (first embodiment) will be described,referring to FIGS. 1 to 4.

In FIG. 1 showing a mechanical system of a gas turbine power plant ofthe first embodiment, A1, B each denote humidified air containing waterof a desired quantity or more or a relative humidity of a desired valueor more, 1 denotes a compressor for compressing air, such as atmosphericair or gas (hereunder, referred to simply as air) that air or oxygen ismain, 2 denotes a spray device for injecting or spraying a coolingmedium such as water or steam onto compressed air, 3 denotes aregenerative heat exchanger for recovering the heat of exhaust gasexhausted from a turbine, 4 denotes a spray device composed of, forexample, a spray nozzle or nozzles or the like for injecting or sprayingthe cooling medium in the humidified air, 5 denotes a combustor formixing and burning fuel and the humidified air to produce combustiongas, 6 denotes fuel such as natural gas which is liquified natural gaswhich is gasified, 7 denotes a turbine operated with the combustion gas,C denotes exhaust gas exhausted from the turbine, 9 denotes a feedwaterheater heating feedwater by using the heat of exhaust gas exhausted fromthe turbine, 10 denotes air or the like, A denotes compressed aircompressed by the compressor, 12 denotes a gas/gas heat exchanger forheat-exchanging the exhaust gas exhausted from the feedwater heater andthe exhaust gas from which humidity thereof is removed at a waterrecovery unit, 13 denotes the water recovery unit for removing humidityin the exhaust gas, 14 denotes a sea water pump for pumping up seawater, 15 denotes a condensate pump for pressurizing recovery waterrecovered by the water recovery tower, 16 denotes a water treatment unitsuch as demineralizer for purifying the recovery water, 17 denotes afeedwater pump for pressurizing purified recovery water, 18 denotes afeedwater pump for pressurizing recovery water (hereunder, referred toas feedwater) pressurized by the feedwater pump, 19, 27, 38, 39 eachdenote a control valve for controlling a flow rate of feedwater, 20denotes a generator driven by the turbine and generating electric powerby converting mechanical energy to electric energy, 25 denotes anelectric motor or starter driving the turbine connected to the turbineto rotate the turbine until fuel is supplied to the combustor and theturbine rotates by force of combustion gas, 26 denotes a turbine rotor,28 denotes a feedwater pump pressurizing feedwater, 29 denotes anexhaust stack exhausting exhaust gas into the atmosphere, 30 denotes aranching device for branching compressed air and changing a branch ratio(distribution of discharge flows of the compressed air).

An operation of the gas turbine power plant according to the presentinvention will be described hereunder.

The compressor 1 compresses air or the like (if it is atmospheric air,the pressure thereof is about 1 ata) to 15 ata, whereby it is turnedinto compressed air A of relatively high temperature, for example, about400° C. by adiabatic expansion. On a flow line of the compressed air Abetween the compressor 1 and the regenerative heat exchanger 3, thespray device 2 is arranged. The spray device 2 sprays fine waterdroplets on the compressed air A to humidify the compressed air A1 andcool it mainly with evaporation latent heat of the fine water droplets,whereby humidified air A1 of relatively low temperature, for example,about 130° C. is obtained. That is, in the spray device 2, thecompressed air A and the fine water droplets are directly contacted,thereby to humidify and cool the compressed air A1 and increase a flowrate thereof. On the basis of a temperature, pressure, water quantity(or absolute humidity or relative humidity) taken as a controlindication, a spray quantity of fine water droplets, that is, a flowrate of feedwater supplied to the spray device 2 is controlled by thecontrol valve 19 so that all the sprayed fine water droplets evaporateand the temperature of humidified air A1 is sufficiently lowered to adesired temperature. In order to avoid damage of piping forming a flowline for the humidified air A1, it is preferable for the humidified airA1 that the relative humidity ψ is a little less than in a saturated aircondition (relative humidity ψ=1). A quantity of fine water dropletssprayed by the spray device 2 is about 11% by weight of the air 10 to besucked into the compressor 1, for example. Further, as a cooling mediumfor cooling the compressed air A by the spray device 2, steam of lowertemperature, preferably, saturated steam, than the compressed air A issufficient, but liquid phase water is preferred to because it has a highcooling effect and it is easy to raise the pressure and to control aflow rate thereof.

Further, on the flow line for the compressed air A between thecompressor 1 and the spray device 2, the branch device 30 is arranged,and a bypass line is arranged, which bypasses the spray device 2 andleads the compressed air A to the regenerative heat exchanger 3. Thebranch device 30 changes a share of a flow rate of compressed air A tobe introduced into the spray device 2 or a flow rate of the compressedair A to be bypassed the spray device 2, whereby the temperature or/andwater quantity of the humidified air A1 at the inlet of the regenerativeheat exchanger 3 can be controlled.

The regenerative heat exchanger 3 which is of 9 type of counter flow andindirect heat exchange, for example, multi tube type, fin tube type,blade fin type, blade type, etc. is arranged at a downstream side of theturbine 7 and at an upstream side of the exhaust stack with respect to aflow of the exhaust gas C. A part or all of the humidified air A1 isintroduced into the regenerative heat exchanger 3 and recovers the heatof the exhaust gas C which has a temperature of about 600° C. or more atthe outlet side of the turbine 7. That is, in the regenerative heatexchanger 3, the humidified air A1 exchanges heat thereof with theexhaust gas C and is heated by the heat of the exhaust gas C to raisethe temperature. The regenerative heat exchanger 3 has a spray nozzle 4arranged at least at one position of the flow line for the humidifiedair A1 in the inside thereof, for example, inside the flow line in aheat conducting tube. The spray nozzle 4 sprays further fine waterdroplets onto the humidified air A1 to obtain humidified air B of about580° C., for example. A spray quantity of the fine water droplets, thatis, a flow rate of feedwater to be supplied to the spray nozzle 4 iscontrolled by the control valve 27, on the basis of one or both of thetemperature, pressure of the humidified air B at the inlet of thecombustor 5 and a temperature difference between the exhaust gas 8flowing in the flow line to the regenerative heat exchanger 3 and thehumidified air B. A quantity of fine water droplets sprayed by the spraynozzle 4 is about 5% by weight of the air 10 introduced into thecompressor 1. Further, a cooling medium for cooling the humidified airA1 by the spray nozzle 4 can be steam, preferably, saturated steam of atemperature lower than the humidified air A1, however, preferably it isliquid phase water having a cooling effect that is high because itreceives latent heat during evaporation and it is easy to raise thepressure and to control a flow rate thereof.

The humidified air B is used as a combustion support gas in thecombustor 5, a working medium gas for the turbine 7, etc. That is, thehumidified air B is introduced into the combustor 5 and mixed with fuel6 in the combustor 5, and the mixture is burnt to produce combustiongas, which is a working medium for the turbine 7, of a temperature of1200° C. or higher. The combustion gas is introduced into the turbine 7to drive it. The turbine 7 is connected to the generator 20 by theturbine rotor 26 to rotate the generator 20, thereby to generateelectric power. The turbine rotor 26 is connected to the compressor 1 todrive it, thereby to compress air 10 or the like. Further, sincecombustion in the combustor 5 becomes unstable at a time of starting ofthe plant or during operation at a low load, it is preferable that thecompressed air A is directly introduced into the combustor to reduce therelative humidity of combustion air.

The feedwater heater 9 of 9 counter flow and indirect heat exchange typeis arranged at a downstream side of the regenerative heat exchanger 3with respect to the flow of exhaust gas C. Water to be supplied to thespray device 2 and spray nozzle 4 is preheated by the heat of exhaustgas C in the feedwater heater 9, and then the water is supplied to eachof the spray device and supply nozzle. Thereby, the remaining of theheat of exhaust gas C recovered by the regenerative heat exchanger 3 canbe recovered, whereby the thermal efficiency of the plant can beimproved. At this time, it is unnecessary to make the temperature of thespray device 2 equal to that of the spray nozzle 4. In the firstembodiment, “the temperature of supply water to the spray device 2”<“thetemperature of supply water to the spray nozzle 4”. For example, thetemperature of supply water to the spray device 2 is about 70° C. andthat to the spray nozzle 4 is about 100° C.

The temperature of exhaust gas C, after the heat thereof is recovered bythe regenerative heat exchanger 3 and the feedwater heater 9, becomesabout 100 to 110° C. at the outlet of the feedwater heater 9, and thenthe exhaust gas C is led to the gas/gas heat exchanger 12. In thegas/gas heat exchanger 12, the exhaust gas exhausted from the feedwaterheater 9 and the exhaust gas C exhausted from the water recovery unit 13are heat-exchanged, whereby the exhaust gas from the feedwater heater 9is cooled and the exhaust gas from the water recovery unit 13 is heated.That is, the exhaust gas C exhausted from the feedwater heater 9 isintroduced into the water recovery unit 13 after being precooled at thegas/gas heat exchanger 12. In the water recovery unit 13 of indirectheat exchange type, the exhaust gas is cooled with a cooling medium suchas low temperature air, sea water, etc. to about 30-40° C. to condenseand recover the water contained in the exhaust gas C. Further, the waterrecovery unit 13 can be of a direct heat exchange type in which coolingwater is directly contacted with the exhaust gas C to cool it. In thiscase, it is possible that a part or all of the water recovered by thewater recovery unit 13 is raised in pressure by a pump andheat-exchanged with the cooling medium to be cooled, and then the cooledwater is recirculated as cooling water to the water recovery unit 13.

The recovery water recovered by the water recovery unit 13 is raised inpressure by the condensate pump 15 and purified by the water treatmentunit 16, and then it is further raised in pressure by the feedwater pump17. The feedwater raised in pressure is led to the feedwater heater 9,preheated there and supplied to the spray device 2 and spray nozzle 4.In this manner, because of recirculation of the water inside the plant,water discharged into the atmosphere is minimized and new water is notoften made up from the outside of the plant.

Alternatively, it is possible to supply the feedwater of low temperatureobtained by raising the pressure by the feed pump 17 to the spray device2, by causing it to bypass the feedwater heater 9. That is, thefeedwater of high temperature heated by the feedwater heater 9 and thefeedwater of low temperature bypassed the feedwater heater 9 are joinedand then supplied to the spray device 2. A flow rate of feedwaterbypassing the feedwater heater 9 is controlled by the control valve 38arranged on the bypassing line, and the temperature of the feedwater tobe supplied to the spray device 2 is controlled by controlling a shareof flow between the feedwater of high temperature heated by thefeedwater heater 9 and the feedwater of low temperature bypassed thefeedwater heater 9. Thereby, in the case where a load of the plantchanges, there is an effect that it is possible to control so as tosuppress lowering in heat recovery efficiency.

Further, alternatively, it is possible to cause the feedwater of lowtemperature obtained by raising pressure by the feedwater pump 17 tobypass the feedwater heater 9 and then supply it to the spray nozzle 4.That is, the feedwater of high temperature heated by the feedwaterheater 9 and the feedwater of low temperature bypassed the feedwaterheater 9 are joined and then supplied to the spray nozzle 4. A flow rateof feedwater bypassing the feedwater heater 9 is controlled by thecontrol valve 39 arranged on the bypassing line, and the temperature ofthe feedwater to be supplied to the spray nozzle 4 is controlled bycontrolling a share of flow between the feedwater of high temperatureheated by the feedwater heater 9 and the feedwater of low temperaturebypassed the feedwater heater 9. Thereby, in the case where a load ofthe plant changes, there is an effect that it is possible to control soas to suppress lowering in heat recovery efficiency.

On the other hand, the exhaust gas C from which water has been recoveredin the water recovery unit 13 is reheated to about 80-90° C. by thegas/gas heat exchanger 12, and then exhausted into the atmospherethrough the stack 29. Reheating the exhaust gas C cooled through heatexchange with sea water to about 80-90° C. prevents the exhaust gas Cexhausted into the atmosphere from causing white smoke. Further, as acold heat medium for condensing water in the exhaust gas C, it ispossible to use the cold heat of liquified natural gas supplied as fuel6 to the combustor 5 or liquified natural gas supplied to equipment suchas another gas turbine plant, iron manufacturing factory, etc.,utilizing the liquified natural gas.

Next, effects of fine water droplet spraying by the spray nozzle 4provided in the regenerative heat exchanger 3 are explained, referringto FIG. 2 and FIG. 3.

In FIG. 2, there are shown relations of plant efficiency and plantoutput to water spray quantities in the regenerative heat exchanger ofthe gas turbine plant. In FIG. 2, an abscissa is water spray quantities(relative values, by weight %, to an air quantity at the outlet of thecompressor) in the regenerative heat exchanger and an ordinate isrelative values of changes, that is, increments of plant efficiency andplant output, to values at the time the water spray quantity is zero inthe regenerative heat exchanger 3.

FIG. 3 shows a relation of exhaust gas temperatures at the outlet of thefeedwater heater 9 to water spray quantities in the regenerative heatexchanger 3 of the gas turbine plant. Further, in FIGS. 2 and 3, thetemperature of exhaust gas C, the temperature of humidified air B at theoutlet of the regenerative heat exchanger 3, an air quantity at theoutlet of the compressor 1 and a water spray quantity of the spraydevice 2 are set constant.

Further, conditional quantities of each fluid of the gas turbine powerplant are shown in table 1.

TABLE 1 Temp. Pressure Flow rate (° C.) (kgf/cm²) (kg/s) Air 10 15  149.5 Compressed air A 393 15 49.5 Spray droplet 70 20 5.5 (spray device2) Humidified air Al 130 14-15 55 Spray droplet 100 20 2.7225 (spraynozzle 4) Humidified Air B 580 14-15 57.7225 Fuel 6 15 — 1.1 Exhaust gasC 650 1-2 59 (re. heat ex. inlet) Exhaust gas C 127 1-2 59 (feed w. heatex. inlet) Exhaust gas C 104 1-2 59 (feed w. heat ex. inlet) (Note: re.,ex. and w. in the table 1 mean regenerative, exchanger and water,respectively.)

From FIG. 2, it is noted that when the water spray quantity in theregenerative heat exchanger 3 is increased from 0 to 5.5% by weight, theplant efficiency is improved by about 5% (relative value) and the plantoutput is increased by about 15%. At this time, from FIG. 3, it is notedthat the temperature of exhaust gas at the outlet of the feedwateroutlet is lowered from about 200° C. to about 100° C. This is becauseincrease in the water spray quantity in the regenerative heat exchangerincreases both a quantity of recovery heat from the exhaust gas C and aflow rate of the humidified air B.

Further, FIG. 4 shows an example of arrangement of the spray nozzles 4in the regenerative heat exchanger 3 of the gas turbine power plantaccording to the present invention.

In FIG. 4, an ordinate is temperature condition of exhaust gas C insidethe regenerative heat exchanger 3 or temperature condition of humidifiedair A1 (at arbitrary scale), and an abscissa is recovery heat quantities(at arbitrary scale) recovered from the exhaust gas C.

In FIG. 4, a straight line a is temperature conditions of exhaust gas Cin which it enters the inlet of the regenerative heat exchanger 3 at atemperature Tgin and the temperature lowers as the recovery heatquantity Q by the humidified air A1 is increasing. A broken line d is astraight line parallel to the line a, showing temperature condition of amedium to be heated in the case where ideal heat recovery from theexhaust gas C can be achieved.

A straight line b is temperature conditions of the humidified air A1when water spray is not effected by the spray nozzle 4. The humidifiedair A1 enters the inlet of the regenerative heat exchanger 3 at atemperature Tab (=Tac), recovers heat from the exhaust gas C and istaken out at the temperature Taout from the outlet of the regenerativeheat exchanger 3 at the temperature Taout. At this time, a flow rate ofthe humidified air A1 is less and the specific heat is also smaller thanthose of the exhaust gas C, so that an inclination is larger than thatof the straight line a and heat recovery quantity Qb corresponding to aposition at the inlet temperature Tab is only Qb. Further, thetemperature at the outlet of the regenerative heat exchanger 3 becomeshigher than Tgb.

On the other hand, a bent line c is a temperature condition ofhumidified air A1 under which water spray is effected inside theregenerative heat exchanger according to the present invention, and inthis case the water spray is effected at 4 positions (spray points SP1,SP2, SP3 and SP4) inside the regenerative heat exchanger 3. Thehumidified air A1 enters the inlet of the regenerative heat exchanger 3at a temperature of Tac (Tab), effects heat recovery from the exhaustgas C and goes out from the outlet of the regenerative heat exchanger 3at a temperature of Taout. In this case, the humidified air whichentered the inlet of the regenerative heat exchanger 3 at a temperatureof Tac (Tab) is raised in temperature in parallel to the straight line bby the heat recovery from the exhaust gas C, however, the water issprayed at the spray point SP1, and the temperature of the humidifiedair A1 is lowered by mainly evaporation latent heat and the flow ratethereof increases. The humidified air A1 is raised in temperature byheat recovery from the exhaust gas C, however, in a similar manner tothe above, it is water-sprayed at the spray points SP2, SP3 and SP4 andthe temperature of the humidified air A1 raised in temperature islowered and a flow rate thereof increases. Thereby, an averageinclination of the bent line c approaches to the ideal straight line d,and a heat recovery quantity corresponding to the inlet temperature Tacincreases to Qc. Further, the temperature of the exhaust gas at theoutlet of the regenerative heat exchanger 3 becomes lower than Tgc.

That is, the water spray in the regenerative heat exchanger 3 canincrease a recovery heat quantity by dQ (=Qc−Qb), and improve the plantefficiency and plant output, as explained in FIG. 2.

Further, if the number of spray points is increased, it approaches moreto the ideal straight line d, and it is possible to further increase arecovery heat quantity.

According to the present embodiment, the following effects can beattained.

(1) By spraying fine water droplets at a downstream side of thecompressor 1 and inside the regenerative heat exchanger 3 and heatingfeedwater to be supplied to the spray device 2 and the spray nozzle 4 bythe feedwater heater 9 when necessary, it is possible to effectivelyeffect heat recovery from the exhaust gas C and increase a flow rate ofthe working medium for the turbine 7, so that it has an effect that theplant efficiency and plant output can be improved.

(2) Further, by spraying fine water droplets at the downstream side ofthe compressor 1 and inside the regenerative heat exchanger 3, anintercooler of the compressor 1 and an aftercooler at the downstreamside of the compressor 1 and further a saturator become unnecessary.Thereby, it is possible to reduce a pressure loss of the working mediumof the turbine 7, and the effects that the plant efficiency and plantoutput are increased are attained. In the conventional saturator unit asdisclosed in JP A 9-264158, since compressed air and falling waterdroplets are directly counter-contacted with each other, a pressure lossis large (for example, 0.3 ata). Further, by using a spray deviceinstead of the saturator unit, such effects are performed that the plantis simplified and small-sized, and the responsivity of control of theplant is improved.

(3) Further, by recirculating water using, as feedwater for the finewater droplet spray, the recovery water which is recovered by condensingwater in the exhaust gas C before being discharged into the atmosphere,new make-up water from the outside is almost not needed and a quantityof water discharged to the atmosphere can be minimized, so that it hasan effect that an influence thereof to circumstances is small.

(4) Further, by controlling spray quantities of fine water droplets tobe sprayed onto the humidified air A1 and humidified air B according tooperational conditions of the turbine, even if the operationalconditions (load, etc.) of the turbine change, it has an effect that ahigh thermal efficiency can be maintained.

Another(second) embodiment will be described, referring to FIG. 5.

In FIG. 5 showing a mechanical system of the gas turbine power plant ofthe second embodiment, 21 denotes an air cooler for cooling compressedair, 22 denotes a saturator unit for humidifying the compressed air, 23and 24 each denote a recirculation pump for pressurizing liquid phasewater in the saturator unit and 40 denotes a control valve forcontrolling a flow rate of feedwater.

The second embodiment shown in FIG. 5 has an air cooler 21 and asaturator unit 22 arranged on the flow line of compressed air A betweenthe compressor 1 and the regenerative heat exchanger 3. The compressedair A is introduced into the saturator unit 22 after being cooled by theair cooler 21 and is directly counter-flow-contacted with liquid phasewater heated by the air cooler 21 and the feedwater heater 9 toevaporate a part of the water and transfer it to the compressed air A,whereby humidified air A1 of relatively low temperature is attained andthe liquid phase water is lowered in temperature. The liquid phase waterlowered in temperature is taken out from the saturator unit 22 by therecirculation pumps 23 and 24 and returned to the saturator unit 22after being heated by the cooler 21 and the feedwater heater 9. In thesecond embodiment, it is preferable to be “a feedwater temperature tothe saturator unit 22”>“a feedwater temperature to the spray nozzle 4”.

Alternatively, the feedwater pressurized by the recirculation pump 24can be supplied to the spray nozzle 4, bypassing the feedwater heater 9.That is, the high temperature feedwater heated by the feedwater heater 9and the low temperature feedwater bypassed the feedwater heater 9 arejoined to be supplied to the spray nozzle 4. And, the temperature offeedwater to be supplied to the spray nozzle 4 is controlled bycontrolling a flow rate of the feedwater bypassing the feedwater heater9 by the control valve 40 arranged on the bypass line and controlling aflow distribution of the high temperature feedwater heated by thefeedwater heater 9 and the low temperature feedwater bypassed thefeedwater heater 9. Thereby, when a plant load changes, there is aneffect that it is possible to effect such a control that reduction ofthermal heat recovery efficiency is suppressed.

On the other hand, the humidified air A1 obtained in the saturator unit22 is introduced into the regenerative heat exchanger 3 arranged in theflow line for exhaust gas C to recover heat from the exhaust gas C as inthe first embodiment shown in FIG. 1, and turned into humidified air Bby spraying fine water droplets on the humidified air A1 by the spraynozzle 4 arranged at at least one position inside the regenerative heatexchanger 3. The humidified air B is used as combustion support gas inthe combustor and as a working medium of the gas turbine 7, etc.

According to the second embodiment, as in the first embodiment, a sprayquantity of fine water droplets of the nozzle 4 is controlled by thecontrol valve 27, on the basis of the temperature, pressure of thehumidified air B at the inlet of the combustor 5, or a temperaturedifference between exhaust gas in the flow line part for exhaust gas Calong the regenerative heat exchanger 3 and humidified air B or boththereof, taken as a control indication, whereby an effect thatresponsivity of the control can be improved irrespective of provision ofwhether the saturator unit 22 of high heat capacity is attained, inaddition to heat recovery of high efficiency according to plantoperational conditions such as partial load, load change, atmospherictemperature, etc. That is, by positively using the spray nozzle 4 it ispossible to improve the responsivity of the control of the plant.

Further, according to the second embodiment, by spraying fine waterdroplets by the spray nozzle 4 it is possible to make a heat recoveryquantity from the exhaust gas C larger as compared with a conventionaltechnique not provided with the spray nozzle 4, so that the feedwaterheater 9 and the saturator unit 22 can be small-sized, whereby a sitearea for the whole plant can be made small and the responsivity can beimproved.

Further, since it is provided with a saturator unit of relative largeheat capacity having a water recirculation line, supply of liquid phasewater to the saturator unit 22 is not stopped instantly because of theinertia of recirculation water even if any trouble takes place in thewater recirculation system, the flow rate and temperature of thehumidified air A1 do not change rapidly, and there is an effect that itis small to impart thermal shock to an equipment such as a turbinesystem, an exhaust gas recovery system, etc.

Further another (third) embodiment will be described, referring to FIG.6.

In FIG. 6 showing a mechanical system of a gas turbine plant of thethird embodiment, A2 denotes humidified air, 31 denotes a spray device(suction air cooler) injecting or spraying water or steam onto airbefore compression, 32 denotes a spray device injecting or sprayingwater or steam onto compressed air A, 33 denotes a control valvecontrolling a flow rate of feedwater, 34 denotes a feedwater pumppressurizing feedwater and 35 denotes a control valve controlling a flowrate of feedwater.

In the third embodiment shown in FIG. 6, the spray device 31 is providedat an inlet of the compressor 1, in addition to the construction of thefirst embodiment. The spray device 31 sprays fine water droplets on air10 or the like. As feedwater for fine water droplet spraying, therecovery water recovered by the water recovery unit 13 is used withoutheating. With this construction, a part of the fine water dropletssprayed by the spray device 31 evaporates to thereby lower thetemperature of air at the suction side of the compressor 1, andremaining of the fine water droplets evaporates inside the compressor 1to lower a temperature of the air, so that power of the compressor 1 canbe reduced, and the thermal efficiency of the plant can be improved.Further, in order to cool the air 10 before compression, it is possibleto arrange a heat exchanger of counter-flow and indirect heat-exchangetype at the inlet of the compressor 1 and effect indirect heatexchanging between an arbitrary cooling medium and the air 10 thereby tocool the air 10.

Further, in the third embodiment, a part or all of the compressed air Afrom the compressor 1 is branched by the branch device 30 and introducedinto the spray device. In the spray deice 32, water of low temperaturerecovered by the water recovery unit 13 is made in fine dropletcondition and sprayed into the compressed air A to obtain humidified airA2 of relatively low temperature. The humidified air A2 is supplied tothe inside of the turbine blades or/and the turbine rotor 26 to cool theturbine blades or/and turbine rotor 26. A spray quantity of fine waterdroplets by the spray device 32, that is, a flow rate of feedwater tothe spray device 32 is controlled by the control valve 35 on the basisof a plant load, a flow rate of fuel 6 or the temperature of combustiongas produced in the combustor 5, taken as a control indication so thatit becomes the temperature of humidified air A2 corresponding to thetemperature of working medium of the gas turbine 7. Thereby, even whenthe temperature of the working medium of the turbine 7 is high (forexample, about 1400° C. or higher), it has an effect that the movingblades and turbine rotor 26, etc. are prevented from suffering fromthermal damage. That is, in the case where the working medium of theturbine 7 contains a lot of steam of large specific heat as in the gasturbine power plant according to the present invention, heat dropaccompanied by expansion of the working medium becomes small, so thattemperatures of the moving blades of the turbine 7, the turbine rotor26, etc. rise. In this third embodiment, as a cooling medium for coolingthe moving blades of the turbine 7 and turbine rotor 26, etc., not dryair but humidified air A2 is used, whereby it is possible to suppressthe temperature elevation, and it is also possible to improve thermalefficiency of the plant without lowering the temperature of the workingmedium at the inlet portion of the turbine 7.

Further, in the third embodiment, the spray device 4 is arranged on theflow line for humidified air B between the regenerative heat exchanger 3and the combustor 5, and fine droplets are sprayed onto the humidifiedair B from the regenerative heat exchanger 3, whereby a moisture contentof the humidified air B is made more greater and a flow rate of workingmedium of the turbine is increased, thereby to improve output of theplant.

Still further another (fourth) embodiment will be described hereunder indetail, referring to FIGS. 7 and 8.

A gas turbine power plant of this embodiment comprises a compressor 1for compressing air to discharge compressed air A, a combustor 5 forburning fuel 6 with humidified compressed air B to produce combustiongas, a turbine 7 driven by the combustion gas from the combustor 5 anddriving the compressor 1 mechanically connected thereto by a rotor shaft26, a generator 20 connected to the turbine 7 by the rotor shaft 26 anddriven by the turbine 7 to generate electric power, a regenerative heatexchanger 3 for heating compressed air A to be supplied to the combustorwith the heat of exhaust gas C of the turbine 7, a first flow line 11 aof a part Aa of compressed air A from the compressor 1, leading to theregenerative heat exchanger 3, a heat exchanger 111 arranged on thefirst flow line 11 a for lowering temperature of the compressed air Aain the first flow line 11 a, a first spray device 201 arranged on thefirst flow line 11 a downstream of the heat exchanger 111 and upstreamof the regenerative heat exchanger 3, a second flow line 11 b of anotherpart Ab of compressed air 11 from the compressor 1, fluidlycommunicating with the heat exchanger 111, and a second spray device 202arranged on the second flow line 11 b for spraying water onto thecompressed air flowing in the second flow line 11 b and humidifying thecompressed air Ab to turn it to humidified air Ab1 lowered intemperature, in which the humidified air Ab1 is heat-exchanged with thecompressed air Aa from the first flow line 11 a in the heat exchanger111.

The regenerative heat exchanger is provided with a water spray 4arranged therein for spraying water droplets onto the compressed airtherein, and the water spray 4 is composed of a plurality of spraynozzles arranged along an air flow pipe of the regenerative heatexchanger 3. The compressed air Aa2 humidified and lowered intemperature by the first spray device 201 enters the regenerative heatexchanger 3 and is heated by exhaust gas C of the turbine 7 while beingsupplied with sprayed water from the water spray 4.

The gas turbine power plant is provided with a third spray device 203 onthe second flow line 11 b downstream of the heat exchanger 111, ifrequired. The humidified compressed air Ab2 heated by the heat exchanger111 is humidified and cooled by the third spray device 203 to be turnedinto humidified air lowered in temperature and led to the regenerativeheat exchanger 3 to join the compressed air Aa2 upstream of the entranceof the regenerative heat exchanger 3.

Further, the gas turbine power plant is provided with a feedwater heater9 downstream of the regenerative heat exchanger 3 with respect to a flowof exhaust gas from the turbine 7, and the above-mentioned water spray 4and the first, second and third spray devices 201, 202, 203 each aresupplied with feedwater heated by the feedwater heater 9, with a flowrate controlled by control valves not shown.

The feedwater is supplied from a water recovery unit 13 in which theexhaust gas cooled by the regenerative heat exchanger 3 and thefeedwater heater 9 is cooled with cooled recirculation water, and steamin the exhaust gas is condensed to become condensate. The condensate isfed to the feedwater heater 9 by a condensate pump 15 and feedwater pump17 through a water treatment apparatus such as a demineralizer 16. Theexhaust gas cooled in the water recovery unit 13 is heated by theexhaust gas from the feedwater heater 9 at the gas/gas heat exchanger 12and then exhausted into the atmosphere through a stack 29.

The recirculation water is recirculated in a line 130 by a recirculationpump 131 and cooled by a cooler 132 with sea water supplied by a seawater pump 14.

With the construction as mentioned above, the compressed air A of hightemperature is divided into two, compressed air Aa and compressed air Abat an outlet of the compressor 1. The compressed air Ab is lowered intemperature sensible heat and heat of evaporation of water sprayed bythe spray device 202 and humidified to be humidified compressed air Ab1of low temperature. The humidified compressed air Ab1 and the compressedair Aa of high temperature are heat-exchanged in the heat exchanger 111,the humidified compressed air Ab1 becomes humidified compressed air Ab2of relatively high temperature and is supplied into the regenerativeheat exchanger 3 at middle stage. When necessary, the humidifiedcompressed air Ab2 can be humidified and lowered in temperature byspraying water by the spray device 203 before entering the regenerativeheat exchanger 3.

The compressed air Aa after the heat exchanging with the humidifiedcompressed air Ab1 becomes compressed air Aa1 of relatively lowtemperature. The compressed air Aa1 is further lowered in temperature bysensible heat and evaporation heat of water sprayed by the spray device201 to become humidified compressed air Aa2 of low temperature andintroduced into the regenerative heat exchanger 3 at the inlet.

That is, in the first embodiment, compressed air of high temperature atthe outlet of the compressor 1 is humidified and lowered in temperatureby directly spraying water, so that the temperature of the compressedair humidified and lowered in temperature is about 130° C. On thecontrary, in the fourth embodiment, one of the divided compressed air Aaand Ab is lowered in temperature through heat exchange with the otherpart of the compressed air and then humidified and lowered intemperature, so that the temperature of humidified compressed air Aa2can be lowered to about 100° C. or less under the same compressor outletair condition as in the first embodiment. By introducing the humidifiedcompressed air Aa2 of low temperature into the regenerative heatexchanger 3, heat can be recovered from the gas turbine exhaust gas Cuntil the temperature of the exhaust gas C becomes sufficiently low,whereby the efficiency of the power plant can be raised.

In FIG. 8, an abscissa is percentages of a flow rate of the dividedcompressed air Aa to a flow rate of the total compressed air at thecompressor outlet, and an ordinate is relative values of increment inpower generation efficiency of the plant to the efficiency when a ratioof flow rate of compressed air Aa is 0. When a ratio of flow rate of thecompressed air Aa is 0, the value corresponds to that in the firstembodiment.

As is apparent from FIG. 8, an increment in the power generationefficiency of the plant increases according to increase in ratio of flowrate of the compressed air Aa, and it becomes maximum about 50% of theflow rate ratio of the compressed air Aa. However, further increase ofthe ratio of flow rate of the compressed air Aa decreases increment inthe power generation efficiency. It is preferable for the ratio of flowrate of the compressed air Aa to be about 50% in order to raise theplant power generation efficiency.

Referring back to FIG. 7, the power plant is provided with an atomizer100 or spray device for atomizing feedwater with compressed airextracted from the compressor. The air to be introduced into thecompressor 1 is humidified by atomized water from the atomizer 100. Thefeedwater for the atomizer 100 is used feedwater not heated by the feedwater heater 9 and pressurized by a feedwater pump 17 a. The provisionof the atomizer 100 enables the air 10 to be humidified, whereby airbeing compressed in the compressor is suppressed a little to rise intemperature.

According to the present embodiment, plant performance, that is, plantpower generation efficiency can be greatly improved, which will beexplained hereunder in comparison with a relevant prior art, forexample, ASME Paper 95-CTP-39 “Humid Air Cycle Development Based onEnergy Analysis and Composite Curve Theory” described in the backgroundof the invention.

In the comparison, a low temperature region heat recovery ability wasstudied. The low temperature region heat recovery ability is as definedlater.

Humidifying and temperature-reducing characteristics of compressoroutlet compressed air, such as low temperature side humidified airtemperature, low temperature region heat recovery ability areillustrated in FIG. 9. In FIG. 9, an abscissa shows flow branch ratios(%) and an ordinate shows temperatures (° C.) of low temperaturehumidifed air and low temperature region heat recovery ability (relativevalue), obtained by the systems of the present embodiment and the priorart.

The flow branch ratios are a ratio of flow rate of compressed air Aa andAb in the present embodiment, and in the prior art a ratio of flow rateof a part of compressed air cooled by the aftercooler, directed to theheat recovery unit by turbine exhaust gas and a flow rate of the otherpart being humidifed and cooling the compressed air in the aftercooler.The characteristic curves Tc are low temperature side humidifed airtemperatures of the present embodiment and the prior art, respectively,and the characteristic curves HRA are low temperature region heatrecovery abilities of the present invention and the prior art,respectively.

An object of obtaining the low temperature humidified air is to enablerecovering heat from the gas turbine exhaust until the exhaust gastemperature becomes as low as possible, and a system is desirable inwhich air of low temperature can be obtained as much as possible.Therefore, in order to compare the heat recovery abilities of the priorart system and the present embodiment in a region where gas turbinetemperature is relatively low, here, the low temperature heat recoveryability is defined as follows:

Low temperature side heat recovery ability=a ratio of a flow rate ofcompressed air flowing to the low temperature humidified air side(branch ratio)

×(gas turbine exhaust gas temperature around the outlet of theregenerative heat exchanger−low temperature side humidifed airtemperature)

×coefficient C. where the gas turbine exhaust gas temperature around theregenerative heat exchanger is set 125° C. Further, the coefficient C isfor adjusting the scale when illustrated, and here the coefficient isset C={fraction (1/20)}.

In the prior art system as shown in FIG. 9, the low temperature regionheat recovery ability defined as above becomes maximum at a flow branchratio of about 50%. However, since the low temperature side humidifiedair temperature rises as the flow branch ratio increases, an incrementin low temperature region heat recovery ability is relatively small.

On the other hand, in the present embodiment, also, the low temperatureregion heat recovery ability as defined above becomes maximum at a flowbranch ratio of about 50%. The low temperature side humidified airtemperature in the present embodiment is constant and about 100° C.until the flow branch ratio reaches about 50%. Further, the lowtemperature side humidified air temperature can be made lower than inthe prior art at a flow branch ratio of about 50%. Therefore, the lowtemperature region heat recovery ability can be made larger than theprior art.

The reason why the low temperature side humidifed air temperature in thepresent embodiment can be made lower at a flow branch ratio of about 50%than in the prior art will be explained under the same condition asabove.

In the prior art system, all the quantity of compressed air (about 300°C.) at the compressor outlet is heat-exchanged with 50% (about 113° C.)of the compressed air humidified and lowered in temperature to getcompressed air lowered in temperature. At this time, a flow rate of thecompressed air that is to heat at the time of heat exchanging is abouttwice as much as a flow rate of the compressed air that is to be heated,the temperature of the compressed air lowered in temperature is reducedto about 210° C. at most , considering temperature efficiency of theheat exchanger. Therefore, the temperature of the compressed air thatthe compressed air of about 210° C. is humidified and lowered intemperature is about 113° C. at most.

On the contrary, in the present embodiment, the compressed air at thecompressor outlet is divided into two flows the flow rates of which are1:1. By humidifying one of the divided compressed air flows, thetemperature of the compressed air can be reduced to about 125° C. Theother divided compressed air flow (about 300° C.) is heat-exchanged withthe divided compressed air (about 125° C.) humidified and lowered intemperature, thereby the compressed air is cooled to about 140° C. Thecompressed air lowered to about 140° C. is small in water content whichis the same as the compressed air at the compressor outlet. Therefore,it is possible to lower the temperature of the compressed to about 100°C. by humidifying it before entering the regenerative heat exchanger.

According to the present embodiment, the heat recovery ability in thelow temperature region can be made larger than that in the prior art, sothat heat can be recovered from the gas turbine exhaust gas until atemperature thereof reaches a low temperature, whereby the plant powergeneration efficiency can be raised. Further, in the case where thetemperature at the outlet of the regenerative heat exchanger is set arelatively high temperature, a temperature difference between theexhaust gas at the outlet of the regenerative heat exchanger and thecompressed air entered there becomes relatively large, so that it has aneffect that the heat conductive area of the regenerative heat exchangercan be made small.

What is claimed is:
 1. A gas turbine power plant having no intercoolerfor compressed air and comprising: a compressor for compressing air; acombustor for burning fuel with compressed air from said compressor toproduce combustion gas; a turbine driven by the combustion gas; agenerator driven by said turbine to generate electric power; aregenerative heat exchanger, heating the compressed air with the heat ofexhaust gas of said turbine and having a water spray arranged thereinfor spraying water droplets onto the compressed air therein; and a spraydevice directly communicating with said compressor for spraying wateronto compressed air of high temperature from said compressor to humidifythe compressed air, the compressed air being led to said regenerativeheat exchanger.
 2. A gas turbine power plant according to claim 1,wherein a feedwater heater is provided downstream of the regenerativeheat exchanger with respect to a flow of exhaust gas from said turbine,and said water spray and said spray device each are supplied withfeedwater heated by said feedwater heater.
 3. A gas turbine power plantcomprising: a compressor for compressing air and discharging thecompressed air; a combustor for burning fuel with the compressed airfrom said compressor to produce combustion gas; a turbine driven by thecombustion gas produced by said combustor; a generator driven by saidturbine to generate electric power; a regenerative heat exchanger forheating compressed air to be supplied to said combustor, using the heatof exhaust gas exhausted from said turbine, said regenerative heatexchanger having a water spray arranged therein for spraying water ontothe compressed air therein; a first flow line for a part of thecompressed air from said compressor, leading to said regenerative heatexchanger; a heat exchanger arranged on said first flow line forlowering temperature of the compressed air in said first flow line; afirst spray device arranged on said first flow line downstream of saidheat exchanger and upstream of said regenerative heat exchanger; asecond flow line for another part of the compressed air from thecompressor, fluidly communicating with said heat exchanger; and a secondspray device arranged on said second flow line for spraying water ontothe compressed air flowing in said second flow line and humidifying thecompressed air to turn it to humidified air lowered in the temperature,the humidified air being heat-exchanged with the compressed air fromsaid first flow line in said heat exchanger.
 4. A gas turbine powerplant according to claim 3, wherein said second flow line is branchedfrom said first flow line between said compressor and said heatexchanger and leads to said regenerative heat exchanger so that thecompressed air led by said second flow line joins the compressed air ledby said first flow line in said regenerative heat exchanger.
 5. A gasturbine power plant according to claim 3, wherein a flow rate ofcompressed air flowing in said first flow line is substantially equal tothat in said second flow line.
 6. A gas turbine power plant according toclaim 3, wherein a third spray device is arranged on said second flowline between said heat exchanger and said regenerative heat exchanger.7. A gas turbine power plant according to claim 6, wherein thecompressed air from said second flow line joins the compressed air fromsaid first flow line at a downstream side of an entrance thereof intosaid generative heat exchanger.
 8. A gas turbine power plant accordingto claim 3, wherein a feedwater heater for heating feedwater with heatof exhaust gas from said turbine is provided at a downstream side ofsaid regenerative heat exchanger with respect to a flow of exhaust gasfrom said turbine, and said water spray is supplied with feedwaterheated by said feedwater heater.
 9. A gas turbine power plant accordingto claim 8, wherein a third spray device is arranged on said ssecondflow line between said heat exchanger and said regenerative heatexchanger, and said first, second and third spray devices each aresupplied with feedwater heated by said feedwater heater.
 10. A gasturbine power plant according to claim 3, wherein an atomizer foratomizing water with compressed air from said compressor is provided forhumidifying air to be sucked into said compressor.